Iost I, Dreyfus M
Laboratoire de Génétique Moléculaire (CNRS D1302), Ecole Normale Supérieure, Paris, France.
Nature. 1994 Nov 10;372(6502):193-6. doi: 10.1038/372193a0.
Eubacterial messenger RNAs are synthesized and translated simultaneously; moreover the speed of ribosomes usually matches that of RNA polymerase. We report here that when in Escherichia coli the host RNA polymerase is replaced by the eightfold faster bacteriophage T7 enzyme for the transcription of the lacZ gene, the beta-galactosidase yield per transcript is depressed 100-fold. But the overexpression of DEAD-box proteins greatly improves this low yield by stabilizing the corresponding transcripts. More generally, it stabilizes inefficiently translated E. coli mRNAs. Ribosome-free mRNA regions, such as those lying behind the fast T7 enzyme or between successive ribosomes on inefficiently translated transcripts, are often unstable and we propose that DEAD-box proteins protect them from endonucleases. These results pinpoint the importance of transcription-translation synchronization for mRNA stability, and reveal an undocumented property of DEAD-box RNA helicases. These proteins have been implicated in a variety of processes involving RNA but not mRNA stability.
真细菌的信使核糖核酸（mRNA）是在合成的同时进行翻译的；此外，核糖体的速度通常与RNA聚合酶的速度相匹配。我们在此报告，当在大肠杆菌中用速度快八倍的噬菌体T7酶替代宿主RNA聚合酶来转录lacZ基因时，每个转录本的β-半乳糖苷酶产量降低了100倍。但是DEAD-box蛋白的过表达通过稳定相应的转录本极大地提高了这种低产量。更普遍地说，它稳定了翻译效率低下的大肠杆菌mRNA。无核糖体的mRNA区域，例如那些位于快速T7酶后面的区域或翻译效率低下的转录本上连续核糖体之间的区域，通常是不稳定的，我们提出DEAD-box蛋白保护它们免受核酸内切酶的作用。这些结果指出了转录-翻译同步对mRNA稳定性的重要性，并揭示了DEAD-box RNA解旋酶的一个未被记录的特性。这些蛋白质已涉及多种涉及RNA但不涉及mRNA稳定性的过程。
